
#ifdef GL_ES
precision mediump float;
#endif

uniform vec2 u_resolution;

float circleshape(vec2 position ,vec2 center, float radius){
    return  step(radius, length(position-center));
}

void main(){
    vec2 position = gl_FragCoord.xy / u_resolution;
    vec3 color=vec3(0.0); 
    vec2 center = vec2(0.5);
    float circle = circleshape(position,center,0.3);
    color = vec3(circle);
    gl_FragColor=vec4(color,1.0);
}